This medallion in Miami, FL, was made with waterjet-cut Lapis Lazuli, Monaco Brown, crosscut travertine, Gold travertine and Russo Levanto.

(Stone World December 96)

With the increasing popularity of waterjet design, it is critical to know the key elements of the specification process

by Richard Ward, P.E. - Richel, Inc

No longer is it an off-the-wall option to have waterjet cut designs in a project. In fact, in many contracts, waterjet cutting is specified and expected. And never before has waterjet cutting been easier to procure.

Any fabrication shop, installer, interior designer or client now has the option of requesting waterjet cut designs in any form and shape by subcontracting to one of several companies located across the states specializing is every aspect of this work.

By simply faxing a sketch or concept to a waterjet specialist, it is possible to have top quality work delivered to your door. In many cases, work is shipped overnight, and with the methods of packing and crating used the designs will reach their destination in perfect condition.

Specify what you need

To ensure standards are met, the following guide lines will help:

Artwork

Who is supplying the art work? Most waterjet contractors offer comprehensive CAD/CAM facilities. This means all the contractor needs to supply is a sketch of the design desired. The clearer the description of the design, the easier it will be for the waterjet contractor to draw and process. Moreover, a clear description of a design will lower the cost for the client.

Specifications - materials

The type of material to be processed will determine the price quoted. As a rule, thicker materials cut more slower than thinner, hence taking more time. Most waterjet contractors ultimately equate every job to the time it will take to cut; hence the longer the time, the greater the price.

The same can be said for the hardness of the materials. For example, granite can take 30%-50% longer to cut than marble. Hence, the same design could vary in price dramatically depending on the material being cut, with the lower costs being in marble, and the greatest in granite. When cutting porcelain, stresses are released in the material, and can result in cracking of the tiles. The cracks can often be eliminated by changing the order in which the design is cut, but on some occasions, are unavoidable. In this case, the only alternative will be to add joints to the design, breaking up the stresses prior to cracking.

Remember to specify who is supplying the materials and how they are being shipped. If buying from a national outlet, it is often cheaper and easier to have the waterjet contractor collect the tiles from the local outlet. If color is not really critical, the waterjet contractor could be asked to procure the materials. However, the safest way to ensure the field tile are the same, is to send the tile to the contractor. This is really easier than it may seem.

One should not place an order purely on cost, of course. Ensure the contractor selected is knowledgeable and experienced in cutting hard surface materials.

Specifications - joint sizes

Specify the joint sizes clearly, both of the field tile and the design itself.

This is critical. The typical and most cost effective joint size of the design will be the kerf width produced by the waterjet. The kerf width depends on the setup of the contractor, but is most commonly 1/16 inch (1.6 mm). This also means the artwork only needs to be done once. If a joint width greater or smaller than the kerf is specified, then the drawings will need to be done twice, or special options will need to be used to compensate for the new joint size. As this requires additional work, the price will increase. For a tighter joint, the waterjet contractor has to cut slower to ensure vertical sides. This means more time - and money.

Field joint sizes vary on every job. An experienced waterjet contractor will know how to adjust for the specified joint width in the most efficient manner. Generally speaking, the field joint size does not effect the pricing. Whenever having waterjet cutting done, it is wise to have the field tile cut at the same time, making it easy for the installer.

Clients have the choice of having joints filled or left open when contracting work out. The most popular option enables the installer to use the same joint material being used on the rest of the job. In terms of aesthetics, this gives the appearance the work was all done on site.

Specifications - assembly instructions

The advantages of having work assembled prior to shipping can be measured in many ways. The obvious factors are saving of time in installation in the field and the ability to assemble work under controlled factory conditions. It is possible to have designs pre-assembled into the original tile size, such as 12- x 12- x 3/8-inch (305 x 305 x 10 cm) tiles, leaving the installer to install the tiles in the normal manner. Each tile is marked and packed in order, enabling the installer to work at the normal pace. With this in mind, it is possible to avoid any additional installation costs.

Care must be taken when specifying the type of epoxy to be used in the assembly process. If any epoxy grout is used, it may be necessary to use an epoxy latex during installation to ensure a good bond - depending on how much natural material is covered with the epoxy. This can be avoided by adding an abrasive material to the epoxy, such as a fine sand sprinkled on top of the epoxy prior to the final setting process on the assembled tile. The abrasive then gives the normal grouts and setting materials something solid to bond to.

To speed up the installation process, it is possible to have work pre-mounted onto cement boards, leaving gaps to line up with the wall studs. Shipping can be easily accommodated, and this option is gaining popularity.

The best way to have alloys installed as part of any work is to have the same waterjet company cut the alloy shapes using the same program. This will ensure good workmanship. The cost will also be less, as the work involved in reproducing the exact shape of a pre-made alloy inlay is enormous and very costly. The final use of the application should be made known, as residential work will vary from commercial, requiring different assembly procedures.

Special Instructions

Knowledge of how the floor will be maintained after installation will direct the waterjet contractor as to any steps that need to be taken based on their experience.

Shipping instructions should be clear. It is important to have the work crated properly as it is doing the work in the first place. By giving the waterjet contractor the installation schedule, real delivery dates can be discussed and secured. The costs involved with waterjet work can be held down by specifying certain materials. For example, sound, thinner materials in marble will cost less than thicker, harder materials such as granite.

To summarize, every company involved in the hard surface industry can promote themselves as a supplier of waterjet cut work. With waterjets now located in many locations throughout the U.S., it is easy to sell the concept, offer clients something unique, easily procure the work, use normal procedures to install the work and increase profits.